Modeling of High-Pressure Adsorption Isotherms above the Critical Temperature on Microporous Adsorbents:  Application to Methane

Bénard, Pierre; Chahine, Richard

doi:10.1021/la960843x

Cited by 101 publications

(87 citation statements)

References 13 publications

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“…Parameter C in the model can be used to calculate the surface area of Zeolite using Eq. (8). The surface area obtained using this method is 438 m 2 /g, which is not significantly different from the one obtained using nitrogen BET surface area.…”

Section: Resultsmentioning

confidence: 55%

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A Simple Technique for Surface Area Determination Through Supercritical Co2 Adsorption

Sudibandriyo¹

2010

MST

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The measurement of specific surface area of porous materials has long been important in physical sciences and is currently growing in importance in applied and environmental science. Numerous systems have been developed for surface area measurement by gas adsorption. Commercial systems are available which can measure a wide range of absolute surface area with relative ease. However, their cost is often prohibitive. In this study, an inexpensive apparatus for surface area measurement has been set up to be used for measuring supercritical adsorption of CO 2 . The Ono-Kondo Lattice model was used to represent the adsorption isotherm and to determine the surface area. The results of surface area determination using CO 2 adsorption combined with OK model have been compared to the numbers obtained from nitrogen BET method. For surface area determination of zeolites and activated carbons, the new method give reasonable agreement results (within 10% deviation) compared to the results obtained from nitrogen BET method. In addition, the new method also gives more reasonable results for surface area determination of coals. As known, the nitrogen BET method gives almost zero of coals' surface area. This might due to the characteristic of the coals' structure that might be change (the pores are closed) during the cooling process in nitrogen BET method. Moreover, the new method can also be used to determine the surface area of porous materials using CO 2 adsorption data at various temperatures without sacrificing their accuracy.

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Section: Resultsmentioning

confidence: 55%

“…The prefactor C i represents the maximum capacity of the adorbent. For pure adsorption inside the slit, according to the approach by Benard and Chahine [8], the number of layers, m, is equal to two, and Eq. (5) becomes:…”

Section: Introductionmentioning

confidence: 99%

A Simple Technique for Surface Area Determination Through Supercritical Co2 Adsorption

Sudibandriyo¹

2010

MST

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“…The commercial, coconut-shell-derived activated carbon CNS-201 (CNS201) was purchased from A.C. Carbon Canada Inc. Because CNS201 is known to be highly microporous, containing 90% of slit pores smaller than 1.3 nm, it is a useful reference material for the microporous ACFs [11]. Argon isotherms were measured at 87 K for ACF10 (0.2811 g) and ACF20 (0.3222 g).…”

Section: Experimental Methodsmentioning

confidence: 99%

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Purewal¹,

Kabbour²,

Vajo³

et al. 2009

Nanotechnology

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Pore size distributions (PSD) and supercritical H 2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H 2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H 2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference.

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“…Actually, the maximum will appear even for high temperatures so long as the pressure is high enough [8] . B nard and Chahine [10] measured the adsorption of methane on CNS-201 carbon over the same range of temperature, but no maximum was observed. The specific surface area of CNS-201 carbon is about half of the AX-21 carbon.…”

Section: Adsorption/desorption Isothermsmentioning

confidence: 97%

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

Zhou

2000

Sc. China Ser. B-Chem.

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Adsorption/desorption isotherms of supercritical methane on superactivated carbon have been measured in the range of 0 10 MPa and 233 333 K (20 K interval). The reversibility of the physical adsorption process is acknowledged. The heat of adsorption of 16.5 kJ/mol is determined from the isotherms, and a new modeling strategy for isotherms with maximum is presented. The model yields fits to the experimental isotherms with precision of 2%, maintaining the constancy of the characteristic energy of adsorption. The exponent of the model equation expresses the pore size distribution feature of the adsorbent. The density of the supercritical adsorbate is evaluated as a parameter of the model. It is shown that the conventional isotherm theory works too at supercritical condition if the limit state of supercritical adsorption is introduced into isotherm modeling.Engineering prospects encouraged studies on the adsorption of supercritical methane on superactivated carbons. One of the impacts of the environment protection law is the development of alternative fuels for vehicles. Natural gas has been an appropriate choice. The on-board storage of natural gas becomes a key technique for such an application. Adsorptive storage of natural gas at ambient temperature and mild pressures shows attractive cost merits in comparison to liquefaction or compressive storage. The superactivated carbon was recognized as the best adsorbent in respects of adsorption capacity and cost. As the major component of natural gas, methane adsorption behavior on the adsorbent will answer questions as to how much gas could be stored on unit mass of carbon or unit volume of tank; how significant is the thermal effect of the adsorption, whether the adsorption process is reversible; etc. The answers to these questions are of the first concern for engineering purposes.The study of methane adsorption on superactivated carbon will contribute to the development Nomenclature E, characteristic energy of adsorption, J mol 1 ; H 0 , enthaply difference between adsorbate phase and ambient gas, kJ mol -1 ; K , the Henry's law constant; n, the measured or excess amount adsorbed, mmol g -1 ; n t , absolute adsorption, mmol/g; n 0 , saturated amount of adsorption, mmol g -1 ; n lim , the limiting amount of supercritical adsorption; P, the equilibrium pressure, MPa; P s , saturated pressure, Mpa; P lim , the limiting pressure of supercritical adsorption, MPa; q, exponent of the Dubinin-Astakhov equation; R, gas constant; T, the equilibrium temperature, K; v a , adsorbate volume, mL g -1 ; U g , density of gas phase, mmol mL 1 ; U a , density of adsorbate phase, mmol mL 1 .

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Modeling of High-Pressure Adsorption Isotherms above the Critical Temperature on Microporous Adsorbents: Application to Methane

Cited by 101 publications

References 13 publications

A Simple Technique for Surface Area Determination Through Supercritical Co2 Adsorption

A Simple Technique for Surface Area Determination Through Supercritical Co2 Adsorption

Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

Measurement and theoretical analysis of the adsorption of supercritical methane on superactivated carbon

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